Media Luna Pupfish

About

The Media Luna Pupfish (Cualac tessellatus) is a small, rarely seen freshwater species native to a single spring system near Media Luna in San Luis Potosi, Mexico, where it inhabits rocky and gravelly substrate amid aquatic vegetation. Its common Spanish name, cachorrito de Media Luna, translates roughly as 'puppy of Media Luna,' a nod to the playful, darting energy typical of pupfishes. Cualac is a monotypic genus, meaning this is the only species it contains, which makes every captive population worth paying attention to from a conservation standpoint. You won't find it at your local fish store, but specialist breeders and hobbyist associations occasionally have it, and supporting those efforts matters. Despite being listed as aggressive and territorial, its behavior in practice tends toward chasing rather than biting, and it can be kept alongside robust hard water species like goodeids or livebearers if needed. Breeding is manageable once you get the water chemistry right. Very hard water is non-negotiable, and many keepers have found that adding chunks of gypsum improves egg development noticeably. It spawns in a fractional pattern, depositing eggs continuously in warm conditions, with fry appearing regularly if sufficient cover is provided. A rewarding project for anyone interested in rare or threatened species.